Numerous approaches have been taken in the removal of certain contaminants from exhaust gases. For example, there has been widespread utilization of catalytic converters in removing certain contaminants or toxic gases from automotive or combustion exhaust emissions. Ion generators have been employed to remove pollutants from exhaust gases and, for example, reference is made to U.S. Pat. No. 3,768,258 to H. W. Smith et al.
In U.S. Pat. No. 4,406,119 to S. Kamiya et al, a wire electrode is utilized in combination with a filter cake for removing contaminants from an exhaust gas stream. Specifically, the electrode serves as a means of electrically heating the gases in order to precipitate out selected particles but also implies utilization of a corona discharge.
In U.S. Pat. No. 4,345,572 and 4,587,807 to N. Suzuki et al, an electrostatic filter pipe connected to a dust connector is used to reduce NO.sub.x in the exhaust gas. U.S. Pat. No. 4,355,504 to B. K. Liu et al is concerned with the collection and removal of particles from an exhaust gas.
U.S. Pat. No. 4,376,637 to L. C. Yang employs an electrode in an exhaust conduit as a means of repelling exhaust particles wherein the electrode is mounted by insulated holding brackets and the particles are repelled by means of a spark discharge through an annular scoop into a discharge grid and filter. U.S. Pat. No. 4,313,739 to D. H. Douglas-Hamilton also utilizes an insulated wire electrode in combination with a porous cylinder for removing contaminants from gases. The primary emphasis in Douglas-Hamilton, however, is utilization of a lower pressure outside of the cylinder to encourage removal of the particles.
Among the most harmful of the gases formed in combustion exhaust of diesel or internal combustion engines is nitrous oxide but, at the same time, is perhaps the most difficult of the toxic gases to efficiently remove. In addition to catalytic converters, scrubbers have been devised to the end of efficient removal of nitrous oxide gases but have not been found to be very practical or efficient for use in automotive, furnace and turbine engines employing hydrocarbon fuels. Molecules, such as, NO, NO.sub.2 and SO.sub.2 are not symmetrical in their structure. They exhibit a permanent dipole moment which is known quite accurately from molecular spectroscopy. Although this dipole moment is small, analysis of the motion of a dipole in an electric field shows that, if the electric field varies as a function of the distance, the dipole will start moving in that direction and describe a path which is directly proportional to the dipole moment and the mass of the molecule. Thus, each molecule which enters the field will move along a fixed path determined by its dipole moment and its mass. Other components of the exhaust, such as, carbon monoxide, water and ozone also have dipole moments. However, since their masses are different, the paths that they follow will also be different. It is therefore important to provide for the efficient removal of NO.sub.x and SO.sub.x molecules from a combustion exhaust stream by reflecting those molecules away from the stream based on their dipole moments and to separately collect or filter out those molecules so that they will not exit or be discharged into the atmosphere with the other gases.